It is generally known to employ apparatus to direct pressurized heated fluid, such as air or steam, into the surface of a moving textile pile fabric to alter location of and/or modify the thermal properties of fibers or yarns contained therein and provide a change in the surface appearance of the fabrics. U.S. Pat. Nos. 2,241,222; 3,010,179 and 3,585,098 disclose apparatus for treating yarn and fiber-containing fabrics by directing a stream or plurality of streams of heated fluid onto the face of the moving fabric from an elongate heated fluid manifold which extends across the path of movement of the fabric.
When heated fluid, such as heated air or steam is applied to the surface of a fabric in one or more streams spaced along an elongate manifold, difficulties are encountered in maintaining uniform temperature of the stream or streams across the full width of the manifold. If pressurized heated fluid is introduced into the manifold from a single location along its length to be discharged from an elongate narrow slot or a plurality of openings extending along the length of the manifold, the varying distances of flow of the fluid through the manifold and from the source of heating of the fluid causes variable temperature losses in the fluid and resultant temperature differences in the fluid streams being discharged from the manifold. When the heat of the fluid in the streams is employed to thermally modify thermoplastic yarns and fibers in the fabrics to cause longitudinal shrinkage and molecular reorientation to produce a desired pattern in the fabric, differences in the temperatures of the streams striking the fabric can produce undesirable irregularities in the pattern applied thereto. It is therefore important to ensure that all streams striking the fabric be of substantially uniform temperature.
Copending commonly assigned Greenway U.S. patent application Ser. No. 103,329, filed Dec. 14, 1979, describes specific apparatus and method for the pressurized high temperature fluid treatment of a moving substrate, such as a textile fabric, with one or more streams of heated fluid discharged into the surface of the moving substrate from an elongate manifold. To provide for more uniform temperature control of the heated stream or streams across the full length of the manifold, pressurized heated fluid, such as air, is directed into the manifold through a plurality of air inlet conduits which communicate at spaced locations along the length of the manifold with the interior manifold compartment. Each of the air inlet conduits is provided with an individual heater, with the heaters and inlet conduits connected in parallel to deliver heated pressurized air into the manifold at uniformly spaced locations along its length. The temperature of air exiting each of the heaters is sensed and controls are provided to monitor and adjust the power supplied to the heaters to compensate for any variations in the heated air entering the manifold compartment from the individual inlet conduits. To individually monitor and continuously control power supplied to each individual heater to maintain exit air temperatures of the heaters uniform requires considerable electrical sensing, monitoring and control equipment, and involves considerable expense in the heat control system of the apparatus.